The present invention relates to the detection of radio frequency emissions resulting from electrical discharges in a rotating machine.
During the operation of generators and motors, various types of malfunctions are associated with electrical discharges, for example in the stator windings of the machine, which discharges produce radio frequency emissions, as well as light emissions.
Such discharges can occur as a result of insulation deterioration or broken conductors or strands. The resulting electrical discharges include insulation partial discharges, insulation corona, slot discharges and gross arcing. Early detection of such discharges can serve to minimize damage so that the necessary repair can be performed at lower cost and with reduced down time for the machine.
Devices have been proposed for monitoring the light emissions associated with such discharges. In addition, various techniques have been proposed for detecting the radio frequency signals resulting from arcing conditions within large electrical machines. The techniques presently employed for radio frequency arc detection require the positioning of a sensor at the neutral lead of the machine. These devices must be placed at a low voltage location on the machine stator winding and must be connected to recording instruments by wires. The location and paths followed by these wires must be carefully selected.
However, for maximum sensitivity of arc detection, it has been found that placement of a sensor at the high voltage end of the stator winding is required, but existing sensors can not be placed at that location while establishing the necessary electrical high voltage isolation for the recording instrument to which it is attached.
A typical microwave radiation monitor employing electrical connectors between the sensing electrodes and the meter is disclosed in U.S. Pat. No. 4,431,965, which issued to Aslan on Feb. 14, 1984. An arc monitor employing fiber optic cables to detect the light emitted by an arc discharge is disclosed in U.S. Pat. No. 4,940,933, which issued of Jenkins on Jul. 10, 1990.